Release of Iron-Loaded Ferritin in Sodium Iodate-Induced Model of Age Related Macular Degeneration: An In-Vitro and In-Vivo Study

• Main Authors: Ajay Ashok (Author), Suman Chaudhary (Author), Aaron S. Wise (Author), Neil A. Rana (Author), Dallas McDonald (Author), Alexander E. Kritikos (Author), Ewald Lindner (Author), Neena Singh (Author)
• Format: Book
• Published: MDPI AG, 2021-08-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

In this report, we evaluated the role of iron in sodium iodate (NaIO₃)-induced model of age-related macular degeneration (AMD) in ARPE-19 cells in-vitro, and mouse models in-vivo. ARPE-19 cells, a human retinal pigmented epithelial cell line, were exposed to 10 mM of NaIO₃ for 24 h, and the expression and localization of major iron modulating proteins was evaluated by Western blotting (WB) and immunostaining. Synthesis and maturation of cathepsin-D (cat-D), a lysosomal enzyme, was evaluated by quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR) and WB respectively. For in-vivo studies, C57BL/6 mice were injected with 40 mg/kg mouse body weight of NaIO₃ intraperitoneally, and their retina was evaluated after 3 weeks as above. We observed that NaIO₃ induced a 10-fold increase in ferritin in ARPE-19 cells, which co-localized with LC3II, an autophagosomal marker, and LAMP-1, a lysosomal marker. A similar increase in ferritin was noted in retinal lysates and retinal sections of NaIO₃-injected mice by WB and immunostaining. Impaired synthesis and maturation of cat-D was also noted. Accumulated ferritin was loaded with iron, and released from retinal pigmented epithelial (RPE) cells in Perls' and LAMP-1 positive vesicles. These observations suggest that NaIO₃ impairs lysosomal degradation of ferritin by decreasing the transcription and maturation of cat-D in RPE-19 cells. Iron-loaded ferritin accumulates in lysosomes and is released in lysosome membrane-enclosed vesicles in the extracellular milieu. Accumulation of ferritin in RPE-19 cells and fusion of ferritin-containing vesicles with adjacent photoreceptor cells is likely to create iron overload, compromising their viability. Moreover, reduced activity of cat-D is likely to promote the accumulation of other cellular debris in lysosomal vesicles, contributing to AMD-like pathology.

Item Description

10.3390/antiox10081253
2076-3921